Circuit for switching d. c. power

ABSTRACT

A circuit for delivering pulsed or constant power to a set of loads, particularly headlamps whose flashing serves as an alert. A number of transistor amplifiers serves as switches to switch moderately high power to the loads from a D.C. source. Two alternating, out-of-phase outputs of a continuously running astable multivibrator bias associated transistor switches into and out of conduction. This causes out of phase pulsed or flashing actuation of loads. An overriding, continuous bias potential, supplied to some, all, or none of the transistor switches, causes steady energization of some, all, or none of the loads. A remote switch controls the delivery of the continuous bias potential to selected transistor switches. When less than all loads operate continuously, the remaining pulsed loads include loads from both out-of-phase groups.

United States Patent 1191 O A e Scarpino Aug. 13, 1974 [54] CIRCUIT FORSWITCHING D. C. POWER 3,732,540 5/1973 Platte 340/83 X [75] Inventor:John J. Scarpino, Garden City, NY. FOREIGN PATENTS OR APPLICATIONS [73]Assignee; Hope-Trunks, Limited, Hempstead, 1,295,979 5/1962 France340/83 NY. [22] Filed: Man 16 1972 Primary Examiner-John W. Caldwell 1Assistant Examiner-Marshall M. Curtis [21] Appl. No.: 235,053

57 ABSTRACT [52] US. Cl 340/81 R, 340/76, 340/83 51 1m. (:1. G08b 5/38 Afor dellvermg Pulsed or Constant POWer a 58 Field of Search 307/41, 247R, 247 A, 315; Set of loads, Particularly headlamps whose flashing 3 5200 A, 09 2 25 340/67, 74, serves as an alert. A number of transistoramplifiers 76, 81 R, 81 F, 82 83 serves as switches to switch moderatelyhigh power to the loads from a DC. source. Two alternating, out-of- 5References Cited phase outputs of a continuously running astable multi-UNITED STATES PATENTS vibrator bias associated transistor switches intoand I out of conduction. This causes out of phase pulsed or 2,663,806 121953 Darlmgton 307 315 flashing actuation ofloads An overridingContinuous 2,891,195 6/1959 Smyth 340/81 R X bias 0t I d t n f th2,994,013 7/1961 Skellett 315/209 R x P Supple 0 some a or 9? e 3 440489 4/1969 Davidson et 315/209 R transistor swltches, causes steadyenergization of 314791641 ll/l969 Summers 340/82 x some, "Oneof theloads- A-femote switch 3,576,527 4/ 1971 Howard 340/6 trols the deliveryof the continuous bias potential to 3,532,930 6 1971 .Marks 340 82 xselected transistor switches. When less than all loads 3,584,257 6/l97lAdams 340/33l UX operate continuously, the remaining pulsed loads in-3,609,681 9/1971 Saul 340/76 clude loads from both out-of-phase groups.3,646,359 2/1972 Bolinger 307/247 A X 3,671,802 6/1972 Ballou 340/76 X 4Claims, 1 Drawing Figure I: f C -5'4 fi m l a 52 '53 i l 1 ER 47 4/ 444: L

g 47 1 45 3 42 5+ 4 11 l l 1 l PATENTEDm: 13 m4 Q g i q CIRCUIT FORSWITCHING D. C. POWER BACKGROUND OF THE INVENTION I This inventionrelates to a circuit for controlling the alternate application ofconstant or pulsed power to several load devices, and more particularlyto a circuit that selectively causes all, less than all, or none of theload devices to be constantly energized while the remainder is pulsed.

For emergency vehicles, police cars, fire vehicles, ambulances, and thelike, flashing headlamps are known to be effective in alerting thepublic, drivers and pedestrians. In other instances, as well, theability to energize one or more electrical devices to receive power at aconstant level or at pulsed or alternating rates may be desired.Examples include audible devices, such as horns, bells, and buzzers.

Drivers of emergency vehicles have been known to flash the headlamp as awarning by rapidly operating the off-on switch by hand. This is adangerous practice in a situation demanding the drivers full attentionand use of both hands. Some automatic flashing arrangement is clearlydesirable.

Circuits using repeatedly opened and closed mechanical switches havebeen proposed. Mechanical switching defects are only too well known,particularly at moderately high current levels. For example, dirty orpitted switch contacts affect both the life and reliability ofmechanical switches. Sparking, when even moderate currents are switched,may limit the use of mechanical switches. This latter defect can bedangerous in the presence of explosive or flammable materials, forexample gasoline at the scene of an accident.

Thermally actuated switches have been tried. In addition to the defectsoutlined above, which result from repeated mechanical making andbreaking of the contacts, thermal actuation suffers furtherdeficiencies. The rate of flash cannot adequately be controlled, andwhen thermal actuation depends on heat generated by the current beingswitched, lamp failure, the drain on the battery from other ordinaryloads, and any other occurrence affecting the current being switchedchange the lamp flashing rate.

Particularly in a circuit that controls the energization of emergencyvehicle lights, the ability to cause pulsating operation of some andconstant operation of others is desirable. If four high beams are usedthese may be operated for normal high beam use. Two may be so operatedleaving two to flash, or all four may be flashed. The low beams can beleft unaffected.

In addition, alternately flashing lamp pairs are particularly effectivealerts. Out-of-phase alternating energization is therefor anotherimportant feature in a circuit which is to be used to flash lamps.

. SUMMARY OF THE INVENTION A control circuit according to this inventionprovides each of the desirable features and capabilities just discussed.Briefly, plural transistor switching arrangements connected betweenplural loads and a source are selectively activated to energize selectedloads. An alternating bias source repeatedly applies bias voltagesappropriate to cause pulsed energization of the loads by repeatedalternations of the transistor switching arrangements between conductionand nonconduction. A manually operable switch applies a constant biasvoltage to all, less than all, or none of the transistor switchingarrangements. The manual switchs constant bias voltage overrides thepulsed signal wherever applied and causes constant or uninterruptedenergization of a load.

The multivibrator has out-of-phase outputs.which provide out-of-phase orwig-wag flashing if applied to transistor switches controlling a pair oflamps. The steady rate at which the multivibrator alternates isindependant of the loads or the currents being switched. The transistorswitching arrangement offers greater reliability than mechanicalswitching, and of course contact sparking is precluded. Amplifierconnections for the transistor switches, Darlington amplifiers in thespecific preferred embodiment that follows, give the transistor switchesa current capability adequate to the initial high current surgecharacteristic of cold headlamp filaments.

The use of an astable multivibrator permits pulse rate adjustment. Thisadds to the flexibility of the circuit. Perhaps more importantly thispermits the rate at which current is switched to a particular set oflamps to be adjusted so that the off time is insufficient to causeexcessive filament cooling. Repeated excessive surges are eliminated andsignificantly less power dissipated. Because the transistor switchingarrangements require only low level signals for actuation, the powerconsumption of the control circuit, itself, is very low.

The manually operable switch controls the mode in which the circuitoperates. If vehicle lamps are controlled, the switch is remote, locatedin the vehicle's passenger compartment. Steady energization of all loadsoccurs when the switch applies the constant overriding bias voltage toall transistor switches. When less than all loads are to be pulsed themanual switch supplies the overriding bias voltage only to thosetransistor switches which supply loads to be operated continuously, andthe multivibrator outputs drive the remaining transistor switches,alternately switching the remaining loads off and on in a pulsed orflashing manner. If all loads are to be pulsed,the manual switchsupplies no signal to any transistor switch.

When four headlamps are controlled and two or four can flash, ablockingdiode connected between the associated pairs of transistor switchesaffords a preferred arrangement to supply the overriding bias to the two.or four lamp control transistor switches. Supplied to one terminal ofthe diode, the bias voltage switches on less than all transistorswitches; supplied to the other, all transistor switches conduct. Asingle two-wire connection to the manual switch in the passengercompartment then simplifies the installation of the circuit. And becausethe manual switch supplies only low currents to control the transistorswitches, light wiring only is brought into the passenger compartment,making switch location and installation easy. g

The control circuit according to the invention also is capable ofswitching a range of voltages and currents, lending versatility to thecircuiLFinally, with appropriate selection of PNP or NPN transistors andassociated circuit components, well within the ordinary artisanscapabilities, the control circuit may be used with either a positive ora negative D.C. supply.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of theinvention, referaccording to the invention as used to control theheadlamps of a vehicle.

DESCRIPTION OF EXEMPLARY EMBODIMENT In the exemplary embodiment shown inthe drawing, a control circuit arranged according'to the invention isgenerally designated by the numeral 10. A battery 11 serves as the DCpower source for the control circuit of the invention. The battery 11maybe an ordinary vehicle battery, serving all of its ordinary uses inaddition to supplying the control circuit according to the invention.The positive terminal of the battery 11 is connected in series with anoff-on headlight control switch 12 which is the ordinary headlightcontrol switch located on a vehicle's dashboard and which is manuallyclosed by a driver to light a vehicles headlights. Also in series withthe battery 11 and the headlight switch 12 is a high beam switch 14. Thehigh beam switch 14 may be conventional, being ordinarily available tooperate the high beam once the headlights have been turned on by closingthe headlight switch 12.

Normally, the switch 14 is connected to each high beam lamp or to thehigh beam filaments of each dual filament lamp and serves directly toactivate the vehicles high beams. However, in the present invention, theswitch 14 supplies power to the control circuit from the contact 14a.The actual application of voltage to the high beam lamps is controlledby the control circuit in the manner described below, once the headlightswitch 12 has been closed and the high beam switch 14 has switched powerto the contact 140 in the high beam on position.

v The circuit 10 controls four lamps, 16, 18, 20, and 22. Forthe"purpose of this discussion, lamps 16 and 18 shall be called the inboardpair, lamp 16 being the left inboard lamp, and lamp 18 being the rightinboard lamp. Lamps 20 and 22 shall be referred to as the outboard pair,lamp 20 being the left outboard lamp and 22 the right outboard lamp.Also the lamps l6 and 18 are illustrated as single filament high beamlamps. Lamps 20 and 22 are dual filament high and low beam lamps withlow beam filaments 23 and 24 in addition to the high beam filaments 25and 26. Voltage to energize the low beam filaments is supplied fromcontact 14b of the high beam switch 14. This arrangement then leaves thelow beam operation unchanged.

' components.

In the switching-arrangement 15, a pair of transistors 01 and Q2 areconnected with the collectors of each transistor in common. The emitterof transistor O1 is connected with line 27 which is '+l2 volts D.C. whenswitches 12 and 14' are closed-Line 27s 12 volt potential is connectedthrough a resistor 28 to both the base of the transistor Q1 and theemitter of transistor'QZ. The base connection 30 of the transistor Q2serves as a trigger or gate connection for the switching arrangement l5,effecting conduction through bothQl and Q2 when an appropriate biaspotential is applied there. So connected, the two transistors form aDarlington amplifier arrangement.

The biasing of the base to emitter voltages of the transistors Q1 and O2is such that the transistors Q1 and Q2 operate in either the cutoff orthe saturation regions. Hence the Darlington amplifiers act essentiallyas switches. The parallel conduction of the transistors Q1 and Q2 makesthis arrangement particularly suitable for headlight control, or forthat matter the control of other moderately high current incandescentlamps. A current capability of 10 amperes is easily attained withcommercially available transistors, and this current capability will beadequate to the current surge which ordinarily occurs when energizingcold incandescent lamp filaments.

A potential at or near ground level applied to the base 30 of thetransistor 02 causes conduction of the transistor switch 15. Therefore,as used herein, bias potential" or bias voltage" is not meant to excludea zero volt connection. A higher positive voltage applied to the baseconnection 30 or an open base connection there blocks conduction throughthe transistor switch 15.

Bias potentials appropriate to cause conduction may be applied to thebase connection 30 via either of two gate paths. Diode 32 and resistor33 form one such path; diode 35 and resistor 36 form another. Thesepaths provide lamp energizing circuit control connections. A ground ornear ground connection to either of these paths will cause thetransistor switch 15 to conduct and lamp 16 to light.

Each of the remaining transistor switches 17, 19, and 21 cooperate withidentical gate paths. Like the individual components of the transistorswitching arrangements, then, the associated gate paths have like diodesand resistors designated by similar reference numerals.

An astable multivibrator 40 operates continuously when switches 12 and14 are closed to activate the control circuit 10. The multivibrator 40controls the flashing rate ofthe lamps when they are flashed. Thecircuitry of the astable multivibrator is conventional and requires nodetailed description other than the general explanation that follows.

In the multivibrator 40, a pair of transistors 03 and 04 are drivenalternately into saturation and cutoff. As the transistor O3 is insaturation, the transistor O4 is in cutoff and vice versa. The rate atwhich the two transistors switch into and out of conduction isselectively controlled by RC networks in the base circuit of therespective transistors. Adjustment of the variable resistors 41 and 42alters the time constants of the RC networks made up of those resistorsand their respective associated capacitors 44 and 45. In addition, apair of capacitors 47 and 48 serve conventionally as filters, and a pairof resistors 49 and 50 establish the collector bias for the transistorsQ3 and Q4, respectively. Resistor 52 is a current limiting resistor andcapacitor 53 smoothes the reference voltage at line 54, holding thatvoltage substantially independent of momentary current changes throughthe multivibrator.

The reference voltage at the line 54 is nearly ground potential.Conduction of the transistor O3 in the multivibrator 40 biases thetransistor switches and 19 into conduction. Conduction of the transistorQ3 opens a current path from the base connection 30 through the firstcontrol connection to the energizing circuit, at the diode 35 andresistor 36, to bias the transistor switch 15 into conduction andsimultaneously opens a current path from the base connection 30 throughthe first control connection to the transistor switch circuit 19, viadiode 35 and the resistor 36" to bias switch 19 into conduction.Conduction of the transistor Q4 acts similarly to bias transistorswitches 17 and 21 into conduction. Because the outputsof themultivibrator 40 are out of phase, the left transistor switches 15 and19 alternate between conducting and blocking'conditions in out-of-phaserelationship to the two right transistor switches 17 and 21. Hence underthe control of the multivibrator 40 lamps l6 and flash in out-of-phaserelationship to the lamps 18 and 22. p

The control of the modes of operation of the control circuit 10 isprovided by a manual mode selector switch 60. This may be any of anumber of commercially available manually operable multiple connectionswitches. For purpose of illustration, the switch 60 is shown to includethree fixed contacts 61, 62 and 63, and a manually operable wiper arm64, connected to ground. In the embodiment shown, the switch 60 is theonly additional element which must be made available to the vehicleoperator.

With the movable wiper arm 64 located in contact with the fixed contact61, control of the four transistor switching arrangements 15, 17, 19,and 21 is left entirely to the astable multivibrator 40. This then isthe first mode of operation in which all four high beam lamps 16, 18,20, and 22 flash.

A second lamp control mode occurs when the movable wiper arm 64 of theswitch 60 contacts the fixedcontact 62 as shown. A ground connection isapplied via line 66 to resistors 33" and 33", which with diodes 32" and32", respectively, form the second control connections of the twoswitching circuits via gate paths to the base connections 30" and 30" oftransistor switches 19 and 21. Now the path to ground from the baseconnections 30" and 30" biases transistor switches 19 and 21 intoconduction continuously, overriding the pulsating or alternating controlof transistors Q3 and Q4 of the multivibrator 40. Lamps 20 and 22 arethus continuously or steadily on in this mode. No continuous path toground is provided to the base connections 30 and 30 of the transistorswitches 15 and 17, a central blocking diode 67 preventing conduction toground via the line 66. Hence the first set of switches 15 and 17continue alternately to conduct, lamps l6 and 18 alternately to flash.

Finally, with the movable wiper arm 64 contacting the fixed contact 63of the mode selector switch 60, a path to ground is completed throughline 68, and the second of the two control connections for eachtransistor circuit, from the base connections 30 and 30' of transistorswitches 15 and 17, and from the base connections 30" and 30" of thetransistor switches 19 and I switch 60 is left with its wiper arm 64 onthe fixed 21, as well, the blocking diode 67 now being forward contacts63, the lights are turned on as usual by closing the headlight switch12, and the high beams are activated in their normal fashion by closingswitch 14. Once this is done, the other two modes of operation areavailable by manual adjustment of the switch 62 to its two positions.

Additional vehicle lamps may be driven from the various transistorswitches as well, and many other uses of the control circuit 10 areavailable. The embodiment of the present invention that is describedabove is intended to be merely exemplary, and those skilled in the artwill be able to make numerous variations and modifications of it withoutdeparting from the spirit and scope of the invention. All suchvariations and modifications embodying the invention are intended to beincluded within the scope of the invention as defined in the appendedclaims.

I claim:

1. A multiple lamp energizing circuit having three lamp energizing modesand including:

a. a first set of at least 2 lamp energizing circuits,

b. a second set of at least 2 lamp energizing circuits,

c. each of said lamp energizing circuits including control meansresponsive to an electrical input signal.

for activating the energizing circuit and each hav-' ing first andsecond control connections, d. a means for producing two alternatingout-ofphase outputs at first and second output terminals,

energizing circuits and conductive in one direction between first andsecond connections,

g. said first output terminal of said alternating producing means beingconnected to the first control connection in at least one and less thanall energizing circuit control means of said first and second sets ofenergizing circuits,

h. said second output terminal of said alternating output producingmeans being connected to the first control connection of the remainingenergizing circuit control means of both sets of energizing circuits,

i. the second control connection of all of the first set of energizingcircuits being connected to the first connection of the unidirectionalconductor means and to said first switch output,

j. the second control connection of all of the second set of energizingcircuits being connected to the second connection of the unidirectionalconductor means and to the second switch output,

whereby in operation, (l) with the selector switch bias applied toneither switch output, said alternating output means activatesenergizing circuits of both sets that are connected with the first inputterminal of the alter-.

nating output producing means, alternately and out of phase with theremaining energizing circuits of both sets that are connected with thesecond output terminal of the alternating output producing means, (2)with the switch bias connection connected'to the first switch output, anoverriding bias is applied to the second control connections of all ofthe circuits in the first set and blocked by the unidirectionalconductor means from the circuits of the second set, to continuouslyactivate only the circuits of the first set while the second setcontinues to be alternately activated out-of-phase, and (3) with thebias connection connected to the second switch output, the overridingbias is applied to the second control connections of all of the secondset of circuits and, via the unidirectional conductor means, to thesecond control connections of the first set to cause all circuitscontinuously to be activated.

2. The lamp energizing circuit according to claim 1 wherein the meansfor producing first and second outof-phase electrical output signals isa continuously run- 8 ning astable multivibrator.

3. The lamp energizing circuit according to claim 1, wherein energizingcircuitsfrom. each of the two lamp energizing circuit sets controlled bythe two out-ofphase outputs are connected with lamps on the oppositesides of a vehicle to cause a distracting out-ofphase flashing.

4. The lamp energizing circuit according to claim 2, wherein each lampenergizing circuit is-connected with a lamp, at least two lampsconnected with the first energizing circuit set are located on oppositesides of a vehicle, and at least. two lamps connected with the secondenergizing circuit set are located on opposite sides of the vehicle,whereby when only the first set of lamp env ergizing circuits are biasedcontinuously into activation, at least one lamp on each side of thevehicle is continuously lighted, while at least one lamp on each side ofthe vehicle flashesl

1. A multiple lamp energizing circuit having three lamp energizing modesand including: a. a first set of at least 2 lamp energizing circuits, b.a second set of at least 2 lamp energizing circuits, c. each of saidlamp energizing circuits including control means responsive to anelectrical input signal for activating the energizing circuit and eachhaving first and second control connections, d. a means for producingtwo alternating out-of-phase outputs at first and second outputterminals, e. a selector switch including
 1. a bias connection,
 2. afirst switch output,
 3. a second switch output, and
 4. means forselectively connecting the bias connection with one of the first output,the second output, and neither output, f. a unidirectional currentconductor means in addition to and distinct from the control means ofthe energizing circuits and conductive in one direction between firstand second connections, g. said first output terminal of saidalternating producing means being connected to the first controlconnection in at least one and less than all energizing circuit controlmeans of said first and second sets of energizing circuits, h. saidsecond output terminal of said alternating output producing means beingconnected to the first control connection of the remaining energizingcircuit control means of both sets of energizing circuits, i. the secondcontrol connection of all of the first set of energizing circuits beingconnected to the first connection of the unidirectional conductor meansand to said first switch output, j. the second control connection of allof the second set of energizing circuits being connected to the secondconnection of the unidirectional conductor means and to the secondswitch output, whereby in operation, (1) with the selector switch biasapplied to neither switch output, said alternating output meansactivates energizing circuits of both sets that are connected with thefirst input terminal of the alternating output producing means,alternately and out of phase with the remaining energizing circuits ofboth sets that are connected with the second output terminal of thealternating output producing means, (2) with the switch bias connectionconnected to the first switch output, an overriding bias is applied tothe second control connections of all of the circuits in the first setand blocked by the unidirectional conductor means from the circuits ofthe second set, to continuously activate only the circuits of the firstset while the second set continues to be alternately activatedoutof-phase, and (3) with the bias connection connected to the secondswitch output, the overriding bias is applied to the second controlconnections of all of the second set of circuits and, via theunidirectional conductor means, to the second control connections of thefirst set to cause all circuits continuously to be activated.
 2. a firstswitch output,
 2. The lamp energizing circuit according to claim 1wherein the means for producing first and second out-of-phase electricaloutput signals is a continuously running astable multivibrator.
 3. Thelamp energizing circuit according to claim 1, wherein energizingcircuits from each of the two lamp energizing circuit sets controlled bythe two out-of-phase outputs are connected with lamps on the oppositesides of a vehicle to cause a distracting out-of-phase flashing.
 3. asecond switch output, and
 4. The lamp energizing circuit according toclaim 2, wherein each lamp energizing circuit is connected with a lamp,at least two lamps connected with the first energizing circuit set arelocated on opposite sides of a vehicle, and at least two lamps connectedwith the second energizing circuit set are located on opposite sides ofthe vehicle, whereby when only the first set of lamp energizing circuitsare biased continuously into activation, at least one lamp on each sideof the vehicle is continuously lighted, while at least one lamp on eachside of the veHicle flashes.
 4. means for selectively connecting thebias connection with one of the first output, the second output, andneither output, f. a unidirectional current conductor means in additionto and distinct from the control means of the energizing circuits andconductive in one direction between first and second connections, g.said first output terminal of said alternating producing means beingconnected to the first control connection in at least one and less thanall energizing circuit control means of said first and second sets ofenergizing circuits, h. said second output terminal of said alternatingoutput producing means being connected to the first control connectionof the remaining energizing circuit control means of both sets ofenergizing circuits, i. the second control connection of all of thefirst set of energizing circuits being connected to the first connectionof the unidirectional conductor means and to said first switch output,j. the second control connection of all of the second set of energizingcircuits being connected to the second connection of the unidirectionalconductor means and to the second switch output, whereby in operation,(1) with the selector switch bias applied to neither switch output, saidalternating output means activates energizing circuits of both sets thatare connected with the first input terminal of the alternating outputproducing means, alternately and out of phase with the remainingenergizing circuits of both sets that are connected with the secondoutput terminal of the alternating output producing means, (2) with theswitch bias connection connected to the first switch output, anoverriding bias is applied to the second control connections of all ofthe circuits in the first set and blocked by the unidirectionalconductor means from the circuits of the second set, to continuouslyactivate only the circuits of the first set while the second setcontinues to be alternately activated out-of-phase, and (3) with thebias connection connected to the second switch output, the overridingbias is applied to the second control connections of all of the secondset of circuits and, via the unidirectional conductor means, to thesecond control connections of the first set to cause all circuitscontinuously to be activated.